Although no major problems are encountered when hermetically joining together the said tapes and the waterproof layer by a welding process, a problem arises when the tapes are to be attached to the fabric of the other layer. This operation necessarily requires making a seam, through the holes of which, although partially occluded by the thread of the seam, water can get in, which defeats the object of using a waterproof zip.
The prior art seeks to avoid this problem by the application of flaps of complicated configuration which, when folded against the zip and the seams, protect the seams, largely mechanically, from water ingress.
This system is not only fiddly to apply but also not very dependable, and is not a one hundred percent reliable solution.